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PDC removal / replacement

Discussion in '1982-Present GM Diesel' started by 6.2Blazer, Jan 23, 2006.

  1. 6.2Blazer

    6.2Blazer 1/2 ton status

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    I posted this awhile back but really did not get any feedback.

    A while back I found a large buildup of oily sludge in the intake and traced it back as coming from a malfunctioning PDC. At the time none of the local autoparts places could get a new PDC so I decided to eliminate it.

    A regular ol' chrome valve cover breather will slip right into place on the existing grommet on the passenger side valve cover. The problem is it pukes engine oil out of it. Since the engine seems to run fine otherwise, and this is an issue on high compression gas engines, I assumed this was a normal issue with the diesel engine. I then tried a valve cover breather that is enclosed with a outlet tube....of course this made the issue worse at it directed the oil spray. I then added a long hose to the outlet to direct the oil but it still makes a mess.....so now......

    I stopped by Jeg's this weekend and they have a valve cover breather that is listed as having an oil seperator built into it. They also have replacement grommets with various shapes/styles of "baffles" built in with the intent of limiting oil passage into the breather.

    Has anybody tried any of these devices to replace the PDC and limit the oil blow-by?
     
  2. imiceman44

    imiceman44 1 ton status

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    Well on mine I just routed a hose down to below the engine and it just has a mist of oil on the underside that I clean once a month.
    Otherwise I have been doing that for 5 years.
    I used to do the same thing with my gas enignes when they start having too much blow by and putting pressure and oil into the carb.
    It runs better with the pressure off.
    It's just a band aid fix
     
  3. 6.2Blazer

    6.2Blazer 1/2 ton status

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    So just a plain hose from the valve cover grommet down, correct? I know Cummins, at least of a few years ago, had a "road draft tube" on the Dodge trucks to route the blowby oil down to the ground (versus all over the engine compartment). However I never paid attention to how it was hooked up (filtered, baffled, etc....).
     
  4. imiceman44

    imiceman44 1 ton status

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    Yep pretty much.
    Don't tell EPA though :haha:
     
  5. Leper

    Leper 1/2 ton status

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    Pipe it into the exhaust...LOL
     
  6. colbystephens

    colbystephens 1 ton status GMOTM Winner

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    sorry, stupid question - what is PDC?
     
  7. kennyw

    kennyw N9PHW Premium Member

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    I believe it is the equivalent of a PCV on a gas motor. Approx 6" dia can on top of the alternator bracket piped into the fill tube...
     
  8. diesel4me

    diesel4me 1 ton status Premium Member

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    Blow-by blues..

    GM calls it a "Crankcase Depression Regulator" in my book..or "CDR"....it has a diaphram in it,not sure if it pulsataes or is just rigid to block excess oil from being directed into the intake..never had to mess with mine,hope I never have to!..

    Gee,I hope your crankcase isn't TOO depressed..:wink1: ..might have to put it on Prozac..:p:

    There was a "baffle" you could install under a W diesels valve cover,to prevent "Runaway"..sometimes an older engine produces enough blowby ,that a diesel will actually RUN ON ITS OWN CRANKASE FUMES!--and speed up to maximum RPM,and NO WAY to shut it down,short of blocking the intake with something real solid,like a thick motors manual,or plywood,etc!..

    THAT would be scary!..especially if your driving in traffic,and it decided to "floor" itself,and refuse to shut off with the key!..:eek1: --I suppose ANY diesel could do the same thing too!..(made me wish I had a remote control cable "intake block off" butterfly,like a choke plate when I had my Jetta,so I could snuff the motor if that ever occured!)..

    I used the "heater hose with the "bowtie" filter run under the truck" trick on many older trucks with excessive blowby..it keeps the air filter from drowning,and also helps keep the plugs from fouling longer..I did tap into the exhaust on one truck and used green silicone HD heater hose to connect it,it worked ok until I was able to put in a better motor..and I hated to swap those motors..they kept my chassis and sheetmetal well oiled,and rust free!..soon as the good non leaky and no blowby motors went in,the trucks rotted away post haste..:mad:
     
  9. 79k20350

    79k20350 3/4 ton status

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    why not direct the oil into a little overflow container?
     
  10. Fubeca

    Fubeca 1/2 ton status

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    A new valve is about $40 from gmpartsdirect.com - :)
     
  11. 6.2Blazer

    6.2Blazer 1/2 ton status

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    I've tried that, but it still blows oil past whatever type of vent you have on the bottle. I also really like the idea of an oil seperator to keep the oil in the crankcase to begin with.
     
  12. maynardogle

    maynardogle 1/2 ton status

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    This one guy on ebay has at least a new valve up for auction seems like all the time... Do search on 6.2 diesel and it comes up.
     

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